Glass nonwoven fabric, glass fiber reinforced plastic molded body, glass chopped strands, and method for manufacturing glass nonwoven fabric

Abstract

To realize a glass nonwoven fabric having high strength, and having practical productivity.SOLUTION: A glass nonwoven fabric (1) has a cross section of a flat shape, and contains a glass filament (10) that satisfies the following conditions (i), (ii), and (iii). (i) The average value of flatness ratios (major axis / minor axis) of the cross section is 1.5 or larger and 8.0 or smaller. (ii) The average value of circle equivalent diameters of the cross section is 5 μm or larger and 20 μm or smaller. (iii) The standard deviation of the circle equivalent diameter is 0.5 or larger and 4.0 or smaller.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a glass nonwoven fabric containing glass filaments. [Background technology]

[0002] In recent years, various studies have been conducted with the aim of further reducing the size or improving the mechanical properties of electrical insulating boards, printed wiring boards, etc. For example, glass nonwoven fabric is used as a reinforcing material for substrates.

[0003] A glass nonwoven fabric containing flat glass fibers has better mechanical properties than a glass nonwoven fabric containing round glass fibers, and therefore has a relatively high strength even when made thin.

[0004] Patent Document 1 describes a glass nonwoven fabric that contains flat glass fibers and is densified without increasing the binder content, while Patent Document 2 describes a glass nonwoven fabric that contains flat glass fibers and a binder, with the binder content being 3 to 8 wt %. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-257042 [Patent Document 2] JP 2004-100142 A Summary of the Invention [Problem to be solved by the invention]

[0006] In response to the increasing demand for further weight reduction and miniaturization of electronic device components, there is a demand for further improvements in the strength and productivity of glass nonwoven fabrics.

[0007] An object of one aspect of the present invention is to provide a glass nonwoven fabric that has high strength and can be produced at a practical level. [Means for solving the problem]

[0008] In order to solve the above problems, a glass nonwoven fabric according to one embodiment of the present invention contains glass filaments that have a flat cross section and satisfy the following conditions (1), (2), and (3): (1) the average flatness ratio (major axis / minor axis) of the cross section is 1.5 or more and 8.0 or less; (2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less; and (3) the standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less.

[0009] Moreover, the glass chopped strand in one embodiment of the present invention has a flattened cross section and contains glass filaments that satisfy the following conditions (1), (2), and (3): (1) the average flattening ratio (major axis / minor axis) of the cross section is 1.5 or more and 8.0 or less; (2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less; and (3) the standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less.

[0010] Moreover, a manufacturing method of a glass nonwoven fabric in one embodiment of the present invention includes a preparation step of preparing glass chopped strands containing glass filaments having a flat cross section and satisfying the following conditions (1), (2), and (3): (1) an average value of the flattening ratio (major axis / minor axis) of the cross section is 1.5 to 8.0; (2) an average value of the equivalent circle diameter of the cross section is 5 μm to 20 μm; and (3) a standard deviation in the distribution of the equivalent circle diameters is 0.5 to 4.0; an opening step of immersing the glass chopped strands in white water and stirring the strands; and a papermaking step of making a glass nonwoven fabric using the white water. Effect of the Invention

[0011] According to one aspect of the present invention, a glass nonwoven fabric having high strength and practical productivity can be realized. [Brief description of the drawings]

[0012] [Figure 1]1 is a partially enlarged optical microscope photograph of a glass nonwoven fabric according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of a glass filament cut along a plane (transverse section) perpendicular to the longitudinal direction. [Diagram 3] 1 is a histogram showing the distribution of the aspect ratio of glass filaments contained in a glass nonwoven fabric according to one embodiment of the present invention. [Figure 4] 1 is a schematic diagram showing a configuration of a glass fiber reinforced plastic molded body in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described. Note that the following description is intended to provide a better understanding of the gist of the invention, and is not intended to limit the present invention unless otherwise specified.

[0014] In one embodiment of the present invention, first, molten glass is drawn out from a bushing and cooled to form a flat fiber having a circle equivalent diameter of several μm to several tens of μm. Next, a treatment agent is applied to the flat fiber and the fibers are bundled to form a strand. The strand is then cut to a predetermined length to obtain a chopped strand.

[0015] Glass fiber is a general term for an aggregate of glass filaments (for example, a bundle of 100 or more filaments) and individual single fibers dispersed from glass fibers (resulting from the opening of glass fibers). The single fibers that make up glass fiber are called glass filaments, an aggregate of multiple glass filament fibers is called a glass strand, and a cut of these to a specified length is called a chopped strand (glass chopped strand).

[0016] In addition, in this specification, the "flatness ratio" means the ratio of the length of the major axis to the length of the minor axis in the shape of the surface to be calculated. The "flatness ratio of the cross section" of the glass filament is used in the following sense. That is, when measuring the flatness ratio of the cross section of the glass filament, the end face of the glass filament is usually observed without cutting the glass filament to form a cross section. In this case, the end face is not necessarily flat, but the shape formed by the outer edge of the end face when the end face is viewed from a line of sight parallel to the longitudinal direction of the glass filament (for example, an ellipse or a rounded rectangle) is regarded as the shape of the "cross section" of the glass filament to calculate the flatness ratio.

[0017] The distribution of the aspect ratio means a frequency distribution, and the distribution of the aspect ratios of a plurality of glass filaments can be grasped, for example, by a histogram in which the horizontal axis is the aspect ratio and the vertical axis is the frequency (number) or relative frequency (mixture ratio). The distribution of the aspect ratio indicates the bias and variation of the aspect ratio in a collection of a specific total number of measurement objects (for example, glass filaments).

[0018] (Brief Description of the Findings of the Invention) Prior to describing the glass nonwoven fabric according to one embodiment of the present invention, the findings of the present inventors will be outlined below.

[0019] Glass nonwoven fabrics are generally manufactured by dispersing a plurality of glass fibers (chopped strands) in white water, followed by papermaking and drying. The glass fibers are dispersed (opened) into aggregates of glass filaments in the white water. Thereafter, the glass filaments may aggregate in the white water over time. If papermaking is performed in a state in which the glass filaments are aggregated, a glass nonwoven fabric with an appearance unsuitable for use as a product will be obtained. Therefore, the worse the dispersibility of the glass fibers in the white water (in other words, the agglomeration resistance), the lower the productivity of the glass nonwoven fabric may be.

[0020] The present inventors have conducted detailed studies on the relationship between the shapes (flattening ratio and equivalent circle diameter) of the chopped strands used in the production of a glass nonwoven fabric and the glass filaments contained in the glass nonwoven fabric, the aggregation resistance of the chopped strands (multiple glass fibers) in white water, and the strength of the resulting glass nonwoven fabric, etc. As a result, they have found that a glass nonwoven fabric with improved performance can be realized by using glass filaments having a flat cross-sectional shape and by setting the flattening ratio and equivalent circle diameter of the glass filaments within a predetermined range.

[0021] By setting the average value of the aspect ratio of the glass filaments contained in the glass nonwoven fabric and the chopped strands within an appropriate range, the glass filaments are less likely to aggregate in white water and the strength of the glass nonwoven fabric can be increased. Glass filaments having a circular cross section are relatively prone to aggregation in white water. In addition, the glass nonwoven fabric is formed by interweaving a plurality of glass filaments, and the larger the bonding area between the plurality of glass filaments, the higher the bonding strength. The glass nonwoven fabric containing glass filaments having a flat cross section has a relatively high tensile strength because the bonding area between the glass filaments can be increased.

[0022] In addition, by setting the average value of the circle-equivalent diameter of the glass filaments contained in the glass nonwoven fabric and the chopped strands within an appropriate range, the aggregation of the glass filaments in the white water can be suppressed and the strength of the glass nonwoven fabric can be increased. For example, if the weight of the chopped strands (i.e., the weight of the glass filaments) added to a certain amount of white water is constant, the following can be said. That is, when the circle-equivalent diameter of the glass filaments is small, the number of glass filaments contained in the white water is larger than when glass filaments with a large circle-equivalent diameter are added to the white water. As a result, the glass filaments become relatively easy to entangle in the white water, and the aggregation start time is shortened. On the other hand, when the number of glass filaments contained in the white water is large, the number of adhesion points between the glass filaments in the glass nonwoven fabric increases, and the tensile strength of the glass nonwoven fabric becomes relatively high.

[0023] Furthermore, it was found that it is also important to set the standard deviation in the distribution of the equivalent circle diameters of the glass filaments contained in the glass nonwoven fabric and the chopped strands within an appropriate range. When the distribution of the equivalent circle diameters of the glass filaments contained in the glass nonwoven fabric and the chopped strands is wide (the standard deviation in the distribution is large), relatively thin glass filaments and relatively thick glass filaments are mixed, and the aggregation start time in white water is likely to be short and the tensile strength of the glass nonwoven fabric is likely to be reduced. This is because relatively thin glass filaments are likely to be entangled in white water, and when the glass nonwoven fabric contains relatively thick glass filaments, the number of bonding points between the glass filaments is reduced, and the tensile strength of the glass nonwoven fabric is likely to be reduced.

[0024] The glass nonwoven fabric in one embodiment of the present invention has been conceived based on the above findings, and can be produced while ensuring resistance to aggregation in white water, and has high strength.

[0025] (Glass nonwoven fabric) Fig. 1 is an optical microscope photograph of a part of a glass nonwoven fabric 1 according to the present embodiment, which is magnified. As shown in Fig. 1, the glass nonwoven fabric 1 is formed by intertwining a plurality of glass filaments 10. The majority of the glass nonwoven fabric 1 according to the present embodiment is formed by the glass filaments 10. In Fig. 1, since it is difficult to image a substance (such as a secondary binder described below) that is translucent to the observation light, images of the glass filaments 10 are mainly shown.

[0026] The glass nonwoven fabric 1 may have a secondary binder and other additive components in addition to the glass filaments 10. The secondary binder may have an ignition loss of 5% by mass or more and 30% by mass or less, or 10% by mass or more and 20% by mass or less. For example, an acrylic resin or an epoxy resin can be used as the secondary binder. The ignition loss can be measured in accordance with JIS R 3420 (2013). The content of other additive components in the glass nonwoven fabric 1 may be 3% by mass or less, or 2% by mass or less. Examples of other additive components include a treatment agent (primary binder) contained in the glass fibers. The treatment agent is dissolved in white water during the manufacturing process, but may be mixed into the glass nonwoven fabric 1 to a certain extent.

[0027] (glass filament) The content of the glass filaments 10 in the glass nonwoven fabric 1 is not particularly limited, but may be, for example, 70% by mass or more and 95% by mass or less, or 80% by mass or more and 90% by mass or less.

[0028] 2 is a cross-sectional view of the glass filament 10 cut in a plane (transverse section) perpendicular to the longitudinal direction. The long diameter of the cross-sectional shape of the glass filament 10 is designated as long diameter L1, and the short diameter is designated as short diameter L2. In this specification, the length of the longest line segment connecting two points on the outer edge in the transverse section of the glass filament 10 is defined as the "long diameter of the glass filament 10," and the length of the longest line segment in the direction perpendicular to the long diameter in the transverse section of the glass filament 10 is defined as the "short diameter of the glass filament 10."

[0029] The cross-sectional shape of the glass filament 10 is not limited to an ellipse. The glass filament 10 may have a flat shape having a non-circular cross section, for example, an oval, an ellipse, or a rounded rectangular shape. The glass filament 10 preferably has an oval flat shape.

[0030] The glass filaments 10 contained in the glass nonwoven fabric 1 in this embodiment satisfy all of the following conditions (1) to (3).

[0031] (1) The average cross-sectional flatness ratio (longer diameter L1 / minor diameter L2) is 1.5 or more and 8.0 or less; (2) The average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less; (3) The standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less.

[0032] Regarding the above (1), when the average value of the aspect ratio of the cross section of the glass filaments 10 contained in the glass nonwoven fabric 1 is less than 1.5, the bonding area between the glass filaments 10 tends to be small, making it difficult to increase the tensile strength. On the other hand, when the average value of the aspect ratio of the cross section of the glass filaments 10 is greater than 8.0, the glass filaments 10 become easily broken, making it difficult to obtain sufficient tensile strength of the glass nonwoven fabric 1.

[0033] Regarding the above (2), if the average value of the equivalent circle diameter of the cross section of the glass filaments 10 contained in the glass nonwoven fabric 1 is less than 5 μm, the glass filaments 10 may break during the papermaking process. On the other hand, if the average value of the equivalent circle diameter of the cross section of the glass filaments 10 contained in the glass nonwoven fabric 1 exceeds 20 μm, the porosity of the glass nonwoven fabric 1 increases and the number of bonding points between the glass filaments 10 decreases. As a result, the tensile strength of the glass nonwoven fabric 1 decreases.

[0034] Regarding the above (3), when the standard deviation in the distribution of the equivalent circle diameters of the cross sections of the glass filaments 10 contained in the glass nonwoven fabric 1 is less than 0.5, hundreds to thousands of glass filaments 10 having a more uniform cross-sectional shape are bundled together, making it difficult for the glass fibers to open in the white water. On the other hand, when the standard deviation in the distribution of the equivalent circle diameters is greater than 4.0, the number of relatively thin glass filaments 10 that are prone to aggregation and the number of relatively thick glass filaments 10 that lead to a decrease in strength are both too large, resulting in a shortened aggregation start time and a decrease in the tensile strength of the glass nonwoven fabric 1.

[0035] The glass nonwoven fabric 1 in this embodiment, containing glass filaments 10 that satisfy the above (1) to (3), has high strength and makes it difficult for the glass filaments to aggregate during papermaking in the manufacturing process (prolongs the time until aggregation begins), thereby providing practical productivity.

[0036] The composition of the glass filaments 10 may be any composition that can produce a glass nonwoven fabric 1 having high strength and practical productivity, and the composition of the glass filaments 10 contained in the glass nonwoven fabric 1 in this embodiment is not particularly limited. The composition of the glass filaments 10 may be, for example, E glass, ECR glass, A glass, AR glass, C glass, D glass, S glass, T glass, NE glass, H glass, etc.

[0037] The glass filaments 10 may have a minor axis L2 in the cross section of 3 to 15 μm, or 5 to 12 μm, and a major axis L1 in the cross section of 10 to 50 μm, or 15 to 30 μm.

[0038] (Aspect ratio distribution) The aspect ratio distribution of the glass filaments 10 contained in the glass nonwoven fabric 1 in this embodiment will be described below. The aspect ratio distribution of the glass filaments 10 contained in the glass nonwoven fabric 1 is approximately the same as the aspect ratio distribution of the glass filaments 10 contained in the chopped strands used in the manufacturing process of the glass nonwoven fabric 1. Therefore, the chopped strands used in the manufacturing process of the glass nonwoven fabric 1 may be used to measure the aspect ratio distribution described below.

[0039] First, the measurement of the flattening ratio distribution will be described. That is, the flattening ratio distribution is measured for a specific total number of glass filaments. This "specific total number" may be the total number of glass filaments 10 whose flattening ratios have been measured, and may be, for example, 1000 or more. Hereinafter, the specific total number may be expressed as N. In order to observe the cross section of the glass filaments 10, the glass filaments 10 are vertically embedded in room temperature curing resin Technovit (manufactured by Kulzer), and polished after the resin has hardened. Next, the cross-sectional shape of the glass filaments 10 is observed with an electron microscope, and the lengths of the major axis L1 and minor axis L2 of the observed glass filaments 10 are measured to calculate the flattening ratio. Then, the specific total number of glass filaments 10 whose flattening ratios have been calculated are classified into a plurality of flattening ratio ranges, and the blending ratio in each flattening ratio range is quantified.

[0040] The glass nonwoven fabric 1 may have the following distribution of the aspect ratio of the glass filaments 10 measured as described above. That is, the ratio of the number of glass filaments classified into a certain aspect ratio category to a specific total number of the glass filaments 10 is defined as the blending ratio, (i) the total blending ratio of the glass filaments 10 having an aspect ratio classified into a flattening ratio category of 1.5 or more and less than 3.0 (hereinafter referred to as the first flattening ratio category A1) is 0 to 20%, (ii) the total blending ratio of the glass filaments 10 having an aspect ratio classified into a flattening ratio category of 3.0 or more and less than 5.0 (hereinafter referred to as the second flattening ratio category A2) is 30 to 70%, and (iii) the total blending ratio of the glass filaments having an aspect ratio classified into a flattening ratio category of 5.0 or more and 8.0 or less (hereinafter referred to as the third flattening ratio category A3) is 30 to 60%. By setting the aspect ratio distribution of the glass filaments 10 as described above, the aggregation resistance of the glass filaments 10 in white water in the papermaking process can be improved, and the strength of the glass nonwoven fabric 1 can be increased.

[0041] Furthermore, it is preferable that the glass nonwoven fabric 1 shows a histogram in which the aspect ratio distribution of the glass filaments 10 includes multiple peaks. This will be described below with reference to Fig. 3. Fig. 3 is a histogram showing the distribution of the aspect ratio of the glass filaments 10 contained in the glass nonwoven fabric 1 of this embodiment.

[0042] The histogram shown in Fig. 3 is a histogram showing the flattening ratio distribution, which is created with the horizontal axis showing the flattening ratio of the glass filaments 10, the vertical axis showing the blending ratio of the glass filaments 10, and a class interval of 0.25. Fig. 3 also shows the cumulative blending ratio (the cumulative relative frequency in the histogram) in each of the above-mentioned first to third flattening ratio categories. The value of the cumulative blending ratio is shown on the right axis. As shown in Fig. 3, the glass nonwoven fabric 1 in this embodiment has at least two peaks in the histogram showing the flattening ratio distribution.

[0043] Here, the glass filaments 10 having a relatively small aspect ratio tend to have a cross section close to a circular shape and a relatively small equivalent circle diameter, and such glass filaments 10 are likely to aggregate in white water as described above. Moreover, the glass filaments 10 having a relatively large aspect ratio tend to have a relatively large equivalent circle diameter, and such glass filaments 10 can reduce the strength of the glass nonwoven fabric 1 as described above. The glass nonwoven fabric 1 in one embodiment of the present invention may contain glass filaments 10 that satisfy the above-mentioned conditions (1) to (3), and further, the standard deviation in the distribution of the aspect ratio of the cross section of the glass filaments 10 contained in the glass nonwoven fabric 1 may be 0.5 to 1.5. According to the above configuration, the proportion (number) of glass filaments 10 having an aspect ratio smaller than the average aspect ratio of the glass filaments 10 and glass filaments 10 having an aspect ratio larger than the average aspect ratio contained in the glass nonwoven fabric 1 can be reduced. Therefore, when the glass filaments 10 are dispersed in white water in the papermaking process, the glass filaments 10 have appropriate dispersibility and good resistance to aggregation, and the strength of the glass nonwoven fabric 1 can be increased.

[0044] The many glass filaments 10 contained in the chopped strands may have various distributions of flatness ratios due to differences in the manufacturing process. For example, the flatness ratio distribution of the strands can be changed by adjusting conditions such as the hole shape (arrangement of holes) of the bushing that draws out the molten glass and various manufacturing temperatures. On the other hand, when two or more types of chopped strands having different medians in the flatness ratio distribution of the glass filaments are simply mixed, the proportion of glass filaments having flatness ratios between the respective medians of the two or more types of chopped strands increases. As a result, chopped strands showing a histogram that does not include a peak (for example, a half-width of 2.0 or more, or no half-width exists) can be obtained. That is, the glass nonwoven fabric 1 in one embodiment of the present invention has improved performance compared to the case where two or more types of chopped strands are simply mixed and dispersed in white water to be made into paper.

[0045] (Circle equivalent diameter distribution) Regarding the circle-equivalent diameter distribution of the glass filaments 10 contained in the glass nonwoven fabric 1 in this embodiment, the circle-equivalent diameter distribution can be measured for a specific total number of a plurality of glass filaments in the same manner as in the above-mentioned method used for measuring the aspect ratio distribution.

[0046] Although not shown in the figure, the glass nonwoven fabric 1 may have a standard deviation in the distribution of the equivalent circle diameter of 0.5 to 4.0, and may exhibit a unimodal histogram.

[0047] Here, the distribution of the flattening ratio and the distribution of the equivalent circle diameter of the glass filaments 10 contained in the glass nonwoven fabric 1 are related to each other. In the manufacturing process of the strands used in manufacturing the glass nonwoven fabric 1, there is usually a relationship in which the wider the distribution of the flattening ratio of the glass filaments 10 contained in the chopped strands, the wider the distribution of the equivalent circle diameter of the glass filaments 10. Therefore, if the glass filaments 10 contained in the glass nonwoven fabric 1 show the above-mentioned distribution of the flattening ratio (a histogram having at least two peaks), it is easy to make the standard deviation in the distribution of the equivalent circle diameter of the glass filaments 10 contained in the glass nonwoven fabric 1 to be 0.5 or more and 4.0 or less.

[0048] (Method of manufacturing glass nonwoven fabric) A method for producing the glass nonwoven fabric 1 in this embodiment will be described below. The method for producing the glass nonwoven fabric 1 in this embodiment includes a preparation step, a fiber-opening step, and a paper-making step.

[0049] The preparation step is a step of preparing a chopped strand containing glass filaments satisfying the above-mentioned conditions (1) to (3). In the preparation step, first, raw materials are weighed to obtain a desired glass composition, and the weighed glass raw materials are melted in a melting furnace. Next, the obtained molten glass is drawn out as a flat fiber from a platinum bushing. Next, a treatment agent (a glass fiber sizing agent) is applied as a primary binder to the drawn out hundreds to thousands of flat fibers having a circle equivalent diameter of 5 to 20 μm by a roll coater method. After that, the flat fibers are bundled and then wound up on a paper tube placed on a rotating collet to form a wound body. Next, chopped strands are produced by cutting, drying, etc. as necessary. For example, the flatness ratio distribution of the chopped strands can be changed by adjusting the hole shape (hole arrangement) of the bushing from which the molten glass is drawn out and various manufacturing conditions. The chopped strands prepared by the above preparation step also fall within the scope of the present invention.

[0050] The glass fiber, which is a bundle of glass filaments 10 contained in the chopped strand, may have its surface coated with a sizing agent made of an organic material containing components such as aminosilane, urethane resin, acrylic resin, epoxy resin, olefin resin, lubricant, and antistatic agent. The blending ratio of the components of the sizing agent is determined depending on the purpose of use. The mass ratio of the sizing agent to the total mass of the glass filaments 10 and the sizing agent is preferably 0.01 to 0.2 mass%.

[0051] The opening step is a step in which the chopped strands are immersed in white water and stirred. The white water may be any conventionally known white water generally used when making paper from glass fibers, etc., and the specific components of the white water are not particularly limited. The specific components of the white water do not have a significant effect on the tensile strength of the glass nonwoven fabric 1.

[0052] The viscosity of the white water can be measured by a known method, for example, in accordance with JIS Z8803 (2011). The viscosity of the white water may be, for example, 1 to 40 cP, or 1 to 20 cP. The stirring speed after immersing the chopped strands in the white water may be 200 rpm to 500 rpm. For example, the amount of chopped strands added per 500 ml of white water may be 1 g to 100 g. The length of the chopped strands may be 3 mm to 30 mm.

[0053] In the opening process, the chopped strands introduced into the white water are opened, and the glass filaments 10 are dispersed in the white water, causing the white water to become cloudy. Then, as time passes, the glass filaments 10 aggregate in the white water, producing visible aggregates. These aggregates are, for example, about 3 mm in diameter.

[0054] The time from when the chopped strands are added to the white water to when the aggregates are visually observed is determined as the aggregation start time. For example, the aggregation start time (the timing of the generation of the aggregates) may be determined based on photographs or videos taken at a predetermined time interval.

[0055] The papermaking process is a process for making a glass nonwoven fabric 1 using white water in which glass filaments 10 are dispersed and before agglomerates are formed. In the papermaking process, a papermaking machine is used to make the white water in which glass filaments 10 are dispersed, and then a secondary binder is applied by a spray device or the like. The glass nonwoven fabric 1 can then be made by drying. A conventional wet papermaking method may be used as the papermaking process.

[0056] The secondary binder that covers at least a portion of the surface of the glass nonwoven fabric 1 may have an ignition loss of 5% by mass or more and 30% by mass or less, or may have an ignition loss of 10% by mass or more and 20% by mass or less. For example, an acrylic resin or an epoxy resin can be used as the secondary binder. The ignition loss can be measured in accordance with JIS R 3420 (2013).

[0057] In the manufacturing method of the glass nonwoven fabric 1 in this embodiment, it is preferable that A satisfies A×B≧50,000, where A is the time (minutes) at which the chopped strands start to aggregate when immersed in white water having a viscosity of 20 cP and stirred at 200 rpm, and B is the tensile strength (N / 100 mm) of the glass nonwoven fabric 1 obtained by papermaking using the white water.

[0058] (Glass fiber reinforced plastic molding) 4 is a schematic diagram showing the configuration of a glass fiber reinforced plastic molded body 50 in this embodiment. As shown in FIG 4, the glass fiber reinforced plastic molded body 50 has a pair of conductor layers 51 facing each other and a plurality of prepregs 52.

[0059] The prepreg 52 is a member in which the glass nonwoven fabric 1 is impregnated with a resin. The resin may be a thermosetting resin or a thermoplastic resin. Examples of the thermoplastic resin that may be used include polyesters such as polycarbonate, polypropylene, polyamide, polyetherimide, and polyethylene terephthalate (PET). Examples of the thermosetting resin that may be used include epoxy resin, phenol resin, polyimide resin, and unsaturated polyester resin.

[0060] The glass fiber reinforced plastic molded body 50 contains one or more layers of glass nonwoven fabric, and can be manufactured, for example, as follows. First, a desired number of prepregs 52 are placed on one conductor layer 51. Next, the other conductor layer 51 is placed on the opposite side of the laminated prepregs 52 from the one conductor layer 51. Next, the pair of conductor layers 51 are pressed in the direction in which the prepregs 52 are placed. This makes it possible to manufacture a glass fiber reinforced plastic molded body 50 in which a plurality of prepregs 52 (in other words, glass nonwoven fabrics 1) are arranged between the pair of conductor layers 51.

[0061] [Additional notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in the above description are also included in the technical scope of the present invention. EXAMPLES

[0062] Examples of the glass nonwoven fabric according to one embodiment of the present invention will be described below, but the present invention is not limited to these examples.

[0063] First, chopped strands having a length of 13 mm and containing glass fibers of E-glass composition with the aspect ratio distribution adjusted as shown in Table 1 below were dispersed in white water, and the glass nonwoven fabrics of Examples 1 to 7 and Comparative Examples 1 to 4 were produced using a papermaking machine.

[0064] The tensile strength and aggregation start time of the produced glass nonwoven fabric were measured by the measurement methods described below.

[0065] <Tensile strength> The tensile strength was measured in accordance with JIS R-3420 7 4 using a precision universal testing machine (Autograph AGS-X 10 kN, manufactured by Shimadzu Corporation).

[0066] <Aggregation start time> A beaker with an inner diameter of 110 mm was prepared, containing 1000 mL of an aqueous solution of sodium polyacrylate adjusted to a viscosity of 20 cP at 25°C. Next, a two-blade blade with a rotation diameter of 75 mm, height of 30 mm, and thickness of 3 mm was placed at a position 10 mm from the bottom of the beaker, and the two-blade blade was rotated at 200 rpm, and 3 g of chopped strands cut to a length of 13 mm were added to the aqueous solution of sodium polyacrylate. After the chopped strands were opened, the time required for the glass filaments to aggregate was measured. The aggregation was judged by visual inspection.

[0067] (evaluation) In the examples of the glass nonwoven fabric according to one aspect of the present invention, the obtained glass nonwoven fabric was evaluated as having high strength when the tensile strength was 196 N / 100 mm or more, and as having good agglomeration resistance, i.e., having practical productivity, when the agglomeration start time was 150 minutes or more.

[0068] (Test Results) For the glass nonwoven fabrics of Examples 1 to 7 and Comparative Examples 1 to 4, data on the glass filaments contained in the glass nonwoven fabrics and the test results of the above tests are shown in Table 1. In Table 1, the "number of peaks in the aspect ratio distribution" indicates the number of peaks in a histogram showing the aspect ratio distribution.

[0069] [Table 1]

[0070] As shown in Table 1, the glass nonwoven fabrics of Examples 1 to 7, which satisfied all of the conditions (1) to (3) of the present invention, had high strength and were practically manufacturable.

[0071] On the other hand, the glass nonwoven fabrics of Comparative Examples 1 to 4 did not satisfy any of the conditions (1) to (3) of the present invention, and at least either the tensile strength or the cohesion resistance was insufficient. [Explanation of symbols]

[0072] 1. Glass nonwoven fabric 10 Glass filament

Claims

1. The cross section is flattened and contains glass filaments that satisfy the following conditions (1), (2), and (3): The ratio of the number of glass filaments classified into a certain aspect ratio range to the specific total number of the plurality of glass filaments is defined as a blending ratio, (i) the total blending rate of the glass filaments having an aspect ratio classified in a first aspect ratio range of 1.5 or more and less than 3.0 is 0 to 20%, (ii) the total blending rate of the glass filaments having an aspect ratio classified in a second aspect ratio range of 3.0 or more and less than 5.0 is 30 to 70%, and (iii) the total blending rate of the glass filaments having an aspect ratio classified in a third aspect ratio range of 5.0 or more and 8.0 or less is 30 to 60%, A glass nonwoven fabric, in which a histogram showing the distribution of the flatness ratio of the plurality of glass filaments, with the horizontal axis being the flatness ratio and the vertical axis being the blending ratio, and with a class interval of 0.25, has at least two peaks: (1) The average cross-sectional flatness ratio (major axis / minor axis) is 1.5 or more and 8.0 or less; (2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less; (3) The standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less.

2. Further comprising a secondary binder covering at least a portion of the surface of the glass nonwoven fabric; The glass nonwoven fabric according to claim 1, wherein the secondary binder has an ignition loss of 5 to 30% by mass.

3. The glass nonwoven fabric according to claim 1 or 2, wherein the standard deviation in the distribution of the aspect ratio is 0.5 or more and 1.5 or less.

4. A glass fiber reinforced plastic molding comprising at least one layer of the glass nonwoven fabric according to any one of claims 1 to 3.

5. The cross section is flattened and contains glass filaments that satisfy the following conditions (1), (2), and (3): The ratio of the number of glass filaments classified into a certain aspect ratio range to the specific total number of the plurality of glass filaments is defined as a blending ratio, (i) the total blending rate of the glass filaments having an aspect ratio classified in a first aspect ratio range of 1.5 or more and less than 3.0 is 0 to 20%, (ii) the total blending rate of the glass filaments having an aspect ratio classified in a second aspect ratio range of 3.0 or more and less than 5.0 is 30 to 70%, and (iii) the total blending rate of the glass filaments having an aspect ratio classified in a third aspect ratio range of 5.0 or more and 8.0 or less is 30 to 60%, A glass chopped strand, in which a histogram showing the distribution of the flatness ratio of the plurality of glass filaments, with the horizontal axis being the flatness ratio and the vertical axis being the blending ratio, and with a class interval of 0.25, has at least two peaks: (1) The average cross-sectional flatness ratio (major axis / minor axis) is 1.5 or more and 8.0 or less; (2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less; (3) The standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less.

6. A preparation step of preparing a glass chopped strand containing glass filaments having a flat cross section and satisfying the following conditions (1), (2), and (3); (1) The average cross-sectional flatness ratio (major axis / minor axis) is 1.5 or more and 8.0 or less; (2) the average equivalent circle diameter of the cross section is 5 μm or more and 20 μm or less; (3) the standard deviation in the distribution of the equivalent circle diameters is 0.5 or more and 4.0 or less; a fiber-opening step of immersing the glass chopped strands in white water and stirring the strands; A papermaking process of making a glass nonwoven fabric using the white water, The glass chopped strands are The ratio of the number of glass filaments classified into a certain aspect ratio range to the specific total number of the plurality of glass filaments is defined as a blending ratio, (i) the total blending rate of the glass filaments having an aspect ratio classified in a first aspect ratio range of 1.5 or more and less than 3.0 is 0 to 20%, (ii) the total blending rate of the glass filaments having an aspect ratio classified in a second aspect ratio range of 3.0 or more and less than 5.0 is 30 to 70%, and (iii) the total blending rate of the glass filaments having an aspect ratio classified in a third aspect ratio range of 5.0 or more and 8.0 or less is 30 to 60%, A method for producing a glass nonwoven fabric, wherein a histogram showing the distribution of the flattening ratios of the plurality of glass filaments, with the horizontal axis representing the flattening ratio and the vertical axis representing the blending ratio, and with a class interval of 0.25, has at least two peaks.

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